Polypropiolactone is a useful precursor for the production of acrylic acid. Pyrolysis of polypropiolactone yields glacial acrylic acid, which is in high demand for the production of polyacrylic acid-based superabsorbent polymers. One advantage of polypropiolactone is that it can be safely transported and stored for extended periods of time without the safety or quality concerns associated with shipping and storing glacial acrylic acid. Given the size of the acrylic acid market and the importance of downstream applications of acrylic acid, there is a need for improved methods of producing precursors of acrylic acid such as polypropiolactone.
Methods have been described where polypropiolactone (PPL) is prepared via carbonylation of ethylene oxide with carbon monoxide, followed by polymerization of a beta propiolactone (BPL) intermediate. However, this process can create solvent compatibility issues when run as a continuous process, e.g., using the product stream of carbonylation as the BPL feedstock stream for polymerization. For example, optimal solvents used for carbonylation are often orthogonal with optimal solvents for the polymerization step. As such, methods to address such a problem in the art are desired.